Charlie - that sounds right out of the same playbook as the old 'do you want me to watch your dinghy?' trick!

We got this all the time in St Lucia, St Vincent, Bequia, Union etc...if you gave in and paid the little urchins to watch your dinghy then you would return to find them gone, but the dinghy intact. If you didnt then (as we discovered) you would return to find it slashed to ribbons.